1. Field of the Invention
The invention relates to horizontal deflection amplifier systems and more particularly to linear deflection amplifier systems for use in raster scanned cathode ray tube displays requiring a selectively variable scan rate capability.
2. Description of the Prior Art
Prior art horizontal raster scanning cathode ray beam deflection amplifier systems have used linear a.c. coupled correction of resonant scanning circuits for achieving improved sweep linearity, but it has been necessary to achieve display size or magnification control from a separate control element. For example, when a change in display size or in the scan rate was to be commanded, a predetermined bias voltage was inserted to generate the increased or decreased fly back switch voltage in an open loop fashion. The functions of the prior art circuit normally interact so as not to remove certain undesired residual current levels that result in excess power loss and undesired heating of the deflection yoke and other circuit elements. Generally, it is also further desired to reduce the power required to drive such deflection systems, to improve sweep linearity, and to provide a fully compatible display size expand-compress function.